M561 Gama Goat

The M561 or Gama Goat!
This Gama Goat is a 6-wheel drive semi-amphibious vehicle that was produced from 1969 to 1973. While this vehicle didn’t have an enormous production life, in those 5 years, CONDEC was able to build a little more than 15,000 units.

These were conceived during the Vietnam War where fighting on land and water was common place. While the appearance of the vehicle is somewhat deceiving, as it appears a 4 wheeled vehicle is towing a 2 wheeled trailer, this is in fact a single vehicle. The front section of the vehicle was attached to the rear with an articulating joint that gave the Gamma Goat great flexibility. The front could articulate 15 degrees while the rear could articulate 30 degrees. This gave the Goat the ability to handle 45 degrees of articulation.

In addition to the articulation, the approach angle was 62 degrees and the departure angle was 45 degrees. This meant the vehicle could go most anywhere and do most things. Although in practice, the Goat proved to be quite capable on land, but lacked a little in the water.

While the vehicle was classified as a semi-amphibious vehicle, you wouldn’t see any sea launches as the only means of propulsion was via the rotating tires. So, the only water crossing that the Goat was able to handle successfully were rivers with slow or no current, large bodies of still water (lakes), and similar bodies of water where traversing could be done with relatively little to no opposing force (current).

The power plant was a 3 cylinder Detroit Diesel featuring 53 cubic inches per cylinder. The 3-53 Detroit was a two stroke engine that could produce 101 horsepower and 217 lb-ft of torque. This was enough power and with the gearing, the 7,000lbs vehicle could reach speeds of 55 mph.

Ultimately, due to its steering, extremely loud exhaust that exited right behind the driver, difficult maintenance and low operations the contract wasn’t renewed.
http://www.dieselarmy.com/news/past-military-vehicles-the-m561-or-gama-goat/